This invention relates to an interface circuit for processing electrical signals, and more particularly, to an analog/digital (A/D) converter circuit.
In a process control system, various parameters of a predetermined operation along a process must be monitored in order to coordinate/control each operation which makes up the total process, thereby controlling the overall process. These parameters oftentimes take the form of an analog signal, which are inputted to the process control system. In order for a digital processor or digital computer of the process control system to utilize these inputs they must be converted to a digital signal. The analog to digital converter (often times referred to herein as A/D converter) performs this function. Precision A/D converters can be obtained but generally have associated therewith a high cost. The present invention provides a precision A/D converter circuit using inexpensive components. Further the circuit configuration of The present invention minimizes the number of terminals required to interface with the other subsystems or circuits of the system, in particular, with the digital processor.